Piston valve of shock absorber

Abstract

Provided is a piston valve of a shock absorber which can achieve both an effect of varying an attenuation force according to a pressure and an effect of varying an attenuation force according to a frequency region. The piston valve includes: a main valve unit coupled to a lower end of a piston rod formed with an orifice hole, to divide an inside of a cylinder into an extension chamber and a compression chamber, the main valve unit generating an attenuation force according to a difference of pressure between the extension chamber and the compression chamber; and a frequency sensitive valve unit installed at one side of the main valve unit and configured to generate an attenuation force according to a frequency of hydraulic fluid delivered through the orifice hole of the piston rod, wherein the frequency sensitive valve unit is installed within the main valve unit.

What is claimed is: 
     
       1. A piston valve of a shock absorber, comprising:
 a main valve unit coupled to a lower end of a piston rod which has an orifice hole, to divide an inside of a cylinder into an extension chamber and a compression chamber, the main valve unit generating an attenuation force according to a difference of pressure between the extension chamber and the compression chamber; and 
 a frequency sensitive valve unit installed at one side of the main valve unit and configured to generate an attenuation force according to a frequency of hydraulic fluid delivered through the orifice hole of the piston rod; and 
 a valve housing having a space which communicates with the orifice hole and coupled to the lower end of the piston rod, so that the main valve unit is coupled to an outer circumferential surface of the valve housing and the frequency sensitive valve unit is installed in the space of the valve housing, 
 wherein the valve housing has a variable inner diameter so that an inner diameter at which the valve housing and the lower end of the piston rod are coupled is smaller than an inner diameter at which the frequency sensitive valve unit is installed in the space, and 
 the frequency sensitive valve unit is installed within the main valve unit. 
 
     
     
       2. The piston valve of  claim 1 , wherein the valve housing and the main valve unit are integrally formed. 
     
     
       3. The piston valve of  claim 1 , wherein the valve housing comprises:
 a width change portion having a width increasing conically in a downward direction of the hydraulic fluid along a circumferential direction at one side of an inner circumferential surface of the space; and 
 a larger-width portion formed successively to the width change portion toward the opposite side of the coupled portion of the piston rod and the valve housing in the space such that an inner circumferential surface of a lower end of the width change portion is wider than an inner circumferential surface of an upper end of the width change portion. 
 
     
     
       4. The piston valve of  claim 1 , wherein the frequency sensitive valve unit comprises a free piston which vertically divides the space into an upper chamber and a lower chamber, and a pair of elastic members provided at a top side and a bottom side of the free piston, respectively. 
     
     
       5. The piston valve of  claim 4 , further comprising a sub-valve unit coupled to a lower end of the space in the valve housing, the sub-valve unit having at least one orifice formed through the sub-valve unit, wherein the lower chamber and the compression chamber communicate with each other through the at least one orifice. 
     
     
       6. The piston valve of  claim 5 , wherein the at least one orifice includes: an extension orifice formed through a valve body of the sub-valve unit; and an compression orifice formed radially outside of the extension orifice. 
     
     
       7. The piston valve of  claim 5 , wherein the sub-valve unit further includes: a multi-plate disc for opening and closing the extension orifice which is formed at a lower side of the valve body; and a retainer and a washer sequentially stacked below the multi-plate disc. 
     
     
       8. A piston valve of a shock absorber, comprising:
 a main valve unit coupled to a lower end of a piston rod which has an orifice hole, to divide an inside of a cylinder into an extension chamber and a compression chamber, the main valve unit generating an attenuation force according to a difference of pressure between the extension chamber and the compression chamber; 
 a frequency sensitive valve unit installed at one side of the main valve unit and configured to generate an attenuation force according to a frequency of hydraulic fluid delivered through the orifice hole of the piston rod; and 
 a valve housing having a space which communicates with the orifice hole is coupled to the lower end of the piston rod, 
 wherein the valve housing has a variable inner diameter so that an inner diameter at which the valve housing and the lower end of the piston rod are coupled is smaller than an inner diameter at which the frequency sensitive valve unit is installed in the space, 
 the frequency sensitive valve unit is installed within the main valve unit, 
 the main valve unit is coupled to an outer circumferential surface of the valve housing, and 
 the frequency sensitive valve unit is installed in the space of the valve housing.